1. Field of the Invention
The present invention relates to a gauge for a vehicle, and more particularly, to a gauge for a vehicle having a spontaneous light-emission type pointer.
2. Description of Related Art
Gauges for vehicles which use a light-emitting device, such as a light-emitting diode, as a light source for a spontaneous light-emission type pointer are known. Such gauges for vehicles generally include a drive unit which serves as a gauge body for driving a pointer shaft in accordance with a measured value, a dial, a light-guiding member disposed behind the dial for guiding the light for illuminating the characters or scales printed on the dial to the rear surface of the dial, and a pointer fixed to the pointer shaft.
A two-sided printed plate board is fixed to the proximal end of an indicating portion of the pointer. A light-emitting diode, which is the light emitting device serving as a light source, is mounted on the upper surface of the two-sided printed plate board with a pair of lead terminals thereof being electrically and mechanically connected to a conductive pattern of the two-sided printed plate board by, for example, soldering. One end of a pointer stand, made of a conductive material, is fixed to the center of the two-sided printed plate board by caulking in such a manner that the pointer stand is electrically connected to the conductive pattern formed on the upper surface of the two-sided printed plate board connected to one of the lead terminals of the light-emitting diode. The pointer stand has a through-hole into which the distal end of the pointer shaft is tightly fitted.
The drive unit is attached to the rear surface of the light-guiding member in such a manner that the pointer shaft is located at the center of an opening of the dial and at an opening of the light-guiding member by fixing two mounting pieces of the drive unit to the light-guiding member by screws. First and second terminals are respectively mounted on the proximal ends of the mounting pieces. A first spring abutment, made of a conductive material, is fixed to the pointer shaft for connecting the inner end of a first spiral restoring spring for restoring the pointer to a zero indicating position to the pointer shaft. The first spiral restoring spring may be made of phosphor bronze.
Also, an insulating washer, made of an insulating material, is fixedly fitted on the pointer shaft. The insulating washer has a through-hole at the center thereof, and a large-diameter collar at the lower end thereof. The through-hole formed at the center of the insulating washer consists of a small-diameter portion into which the pointer shaft is inserted, and a large-diameter portion into which the large-diameter portion formed on part of the outer periphery of the pointer stand is fitted. A second spring abutment, made of a conductive material, is fixed to the outer periphery of the insulating washer for connecting the inner end of a second spiral spring to the insulating washer. The outer end of the second spiral spring is fixed to the second terminal. The large-diameter collar of the insulating washer is located between the first and second spiral springs in order to prevent contact thereof.
A spring receiver, made of a conductive material, is mounted on the outer periphery of the insulating washer. The spring receiver is in contact with the second spring abutment. A coil spring, made of a metal, is provided between the spring receiver and the under surface of the two-sided print plate board in such a manner that one end of the coil spring is connected to the conductive pattern on the undersurface of the two-sided printed plate board which is in turn connected electrically to the other of the lead terminals of the light-emitting diode. The spring receiver has a vertical wall portion having an inner diameter slightly larger than the outer diameter of the coil spring so that it can receive the coil spring in a stable state. In this way, a predetermined electrical connection is assured and contact of the coil spring with other components is prevented.
Hence, one of the lead terminals of the light-emitting diode is connected to the first terminal through the conductive pattern on the upper surface of the two-sided printed plate board, the pointer stand, the pointer shaft, the first spring abutment, and then the first spiral spring, while the other lead terminal is connected to the second terminal through the conductive pattern on the undersurface of the two-sided printed plate board, the coil spring, the spring receiver, the second spring abutment and then the second spiral spring.
Consequently, a current can be supplied to the light-emitting diode by connecting a power source between the first and second terminals.
The above-described gauge for the vehicle is assembled in the manner described below: the drive unit with the first spring abutment, the first spiral spring, the insulating washer, the second spring abutment, and the second spiral spring incorporated beforehand is first mounted on the light-guiding member, and then the coil spring is mounted through the openings. Thereafter, the pointer stand of the assembled pointer is fitted into the through-hole of the insulating washer while the distal end of the pointer shaft is inserted into the through-hole of the pointer stand, by which the coil spring is provided between the two-sided printed plate board and the spring receiver so as to achieve a predetermined electrical connection.
In the above-described type conventional gauge for a vehicle, a large number of parts which are not associated with the function of the gauge, such as the two-sided printed plate board, the coil spring and the spring receiver, must be incorporated in the gauge to provide power supply to the light-emitting diode, which is the light-emitting device serving as the light source for the spontaneous light-emission pointer, in a way that supply of power does not adversely affect the drive of the pointer of the gauge. Consequently, the number of parts is increased, the assemby property is not good, and good electrical conduction cannot be provided. These result in an increase in the production cost and in imbalance of the pointer.